JP7794872B2 - Carbon dioxide capture equipment - Google Patents

Description

The present invention relates to a carbon dioxide capture device.

Technology that utilizes a heat source such as a heat pump in a system that uses a heat medium to heat or cool target equipment is known. This type of technology is described, for example, in Patent Document 1. Patent Document 1 relates to an energy-saving ventilation and air-conditioning system that maintains an air-conditioned space at a specified temperature and humidity.

JP 2010-276217 A

Incidentally, heat pumps and other heat sources are also used in carbon dioxide capture systems, which capture carbon dioxide by drawing gases such as air containing carbon dioxide into a module that holds an adsorbent, causing the adsorbent to adsorb the carbon dioxide, and then decompressing and heating the adsorbent to desorb the adsorbed carbon dioxide.

In carbon dioxide capture systems, a high-temperature heating medium must be supplied to the adsorption module, while a low-temperature cooling medium must also be supplied to condense the exhaust heat from each device and the recovered water vapor. However, when there is a large temperature difference between the heating medium and the cooling medium, the energy required for heat exchange in the heat source increases, resulting in a decrease in COP (Coefficient of Performance). Carbon dioxide capture systems, which need to supply a heat medium to multiple devices requiring different temperature ranges, have room for improvement in terms of energy efficiency.

The objective of the present invention is to provide a highly energy-efficient carbon dioxide capture device that can efficiently heat and cool even when equipment requiring different temperature ranges is present.

(1) The present invention provides a heat exchanger (e.g., heat exchanger 70 described later) having a heating heat medium line (e.g., hot water line 112 described later) that supplies the heating heat medium (e.g., hot water line 112 described later) to each of the modules for heating, and a cooling heat medium line (e.g., cold water line 111 described later) that supplies the cooling heat medium (e.g., cold water line 111 described later) to each of the modules for cooling, and the heat exchanger has a heating heat medium line (e.g., hot water line 112 described later) that supplies the heating heat medium (e.g., hot water line 112 described later) to each of the modules for heating, and a cooling heat medium line (e.g., cold water line 111 described later) that supplies the cooling heat medium (e.g., cold water line 111 described later) to each of the modules for cooling, and the heat exchanger has a heating heat medium line (e.g., hot water line 112 described later) that stores the heating heat medium heated by the heat source. a heat-source low-temperature water circuit (e.g., heat-source low-temperature water circuit 86) that includes a cooling heat medium tank (e.g., a cold water tank 82) that stores the cooling heat medium cooled in the heat source device and circulates the cooling heat medium between the cooling heat medium tank and the heat source device; and an equipment heat recovery circuit (e.g., equipment heat recovery circuit 87) that branches off from the heat-source low-temperature water circuit and is connected to the inlet side of the heat source device of the heat-source low-temperature water circuit via target equipment (e.g., a vacuum pump 62, a carbon dioxide recovery pump 63, and an intercooler 64) that performs the adsorption process or the desorption process, and returns the cooling heat medium that has recovered exhaust heat from the target equipment to the heat source device.

(2) In the carbon dioxide capture device described in (1) above, the cooling heat medium after recovering the exhaust heat that has cooled the module may be returned to the inlet side of the heat exchange device via the cold water tank.

(3) The carbon dioxide capture device described in (1) or (2) above may further include a cascade pump (e.g., the equipment cooling pump 870 described below) that sends the cooling heat medium to the inlet side of the heat source device.

(4) In the carbon dioxide recovery device described in (1) or (2) above, the equipment heat recovery circuit may be configured so that the target equipment is arranged on each of multiple paths branching from the heat-source low-temperature water circuit, and the cooling heat medium that has recovered exhaust heat from each of the multiple target equipment may be collected and returned to the heat source unit.

(5) The carbon dioxide recovery device described in (1) or (2) above may further include a control device that controls the path of the equipment heat recovery circuit so that the temperature of the cooling heat medium flowing into the heat source device is within a predetermined appropriate range.

The present invention provides a highly energy-efficient carbon dioxide capture device that can efficiently heat and cool even when devices requiring different temperature ranges coexist.

FIG. 2 is a schematic diagram showing a configuration relating to gas flow in a carbon dioxide capture device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration relating to the flow of liquid in the carbon dioxide capture device of the present embodiment. FIG. 2 is a schematic diagram showing the configuration of gas flow in the module of the carbon dioxide capture device of the present embodiment. FIG. 2 is a schematic diagram showing the configuration regarding the flow of liquid in the module of the carbon dioxide capture device of the present embodiment. 1 is a schematic diagram showing the configuration of a heat source circuit of a carbon dioxide recovery device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the connection positions of each line connected to the hot water tank. FIG. 2 is a schematic diagram showing the connection positions of each line connected to the cold water tank. 10 is a graph schematically showing the relationship between the temperature difference of the heat medium introduced into the heat source device and the COP.

Embodiments of the present invention will be described below with reference to the drawings.

<Overall structure>
Fig. 1 is a schematic diagram showing the configuration related to gas flow in a carbon dioxide capture device 1 according to one embodiment of the present invention. Fig. 2 is a schematic diagram showing the configuration related to liquid flow in the carbon dioxide capture device 1 of this embodiment. Note that the configuration related to liquid flow in the carbon dioxide capture device 1 is omitted from Fig. 1, and the configuration related to gas flow in the carbon dioxide capture device 1 is omitted from Fig. 2.

The carbon dioxide capture device 1 of this embodiment is applied to direct air capture (DAC) technology, which captures carbon dioxide from the atmosphere in order to reduce the carbon dioxide concentration in the atmosphere. The carbon dioxide captured by the carbon dioxide capture device 1 can be stored underground or reused as fuel or material.

As shown in Figures 1 and 2, the carbon dioxide capture device 1 of this embodiment includes a module unit 10, a fan 61, a vacuum pump 62, a carbon dioxide capture pump 63, an intercooler 64, a separator 65, a carbon dioxide tank 66, an inert gas tank 69, a heat exchanger 70, and a control device 90.

As shown in Figure 1, the carbon dioxide capture device 1 has an adsorption line 101, a vacuum line 102, a carbon dioxide line 103, a circulation line 104, and an inert gas supply line 107 as gas flow paths.

The module unit 10 is composed of multiple modules 11 that adsorb carbon dioxide arranged in parallel. In this embodiment, a total of 16 modules 11 are arranged using a pair of left and right module units 10.

Figure 3 is a schematic diagram showing the gas flow configuration of the module 11 of the carbon dioxide capture device 1 of this embodiment. The module 11 is a carbon dioxide capture module that includes an adsorbent 12, a first valve 21, a second valve 22, a third valve 23, a fourth valve 24, a pressure sensor 25, a carbon dioxide sensor 26, and a temperature sensor 27.

The adsorbent 12 is placed inside the module 11 to adsorb carbon dioxide. The adsorbent 12 is a particulate material that adsorbs carbon dioxide at low temperatures (e.g., in the range of -30°C to 50°C) and desorbs (releases) carbon dioxide at high temperatures (e.g., in the range of 50°C to 110°C) when the ambient carbon dioxide concentration is low. Examples of such adsorbents 12 include solid amine carbon dioxide adsorbents constructed by supporting amines on porous materials such as silica.

The first valve 21 is an on-off valve located at the connection between the carbon dioxide line 103, which captures carbon dioxide, and the module 11. A carbon dioxide capture pump 63 is located on the carbon dioxide line 103. The second valve 22 is an on-off valve located at the connection between the vacuum line 102, in which the vacuum pump 62 is located, and the module 11. The third valve 23 is an on-off valve located at the inlet that takes in atmospheric air and the like into the interior of the module 11. The fourth valve 24 is an on-off valve located at the connection between the adsorption line 101 and the module 11.

The first valve 21, second valve 22, third valve 23, and fourth valve 24 are all controlled to open and close by the control device 90. The first valve 21, second valve 22, third valve 23, and fourth valve 24 are, for example, normally open butterfly valves.

The pressure sensor 25 measures the internal pressure of the module 11. The carbon dioxide sensor 26 measures the carbon dioxide concentration inside the module 11. The temperature sensor 27 measures the temperature of the adsorbent 12. Measurement information from the pressure sensor 25, carbon dioxide sensor 26, and temperature sensor 27 is sent to the control device 90.

Returning to Figure 1, the adsorption line 101 and fan 61 will now be described. The adsorption line 101 is branched and connected to each of the modules 11. The fan 61 is located where the branched portions of the adsorption line 101 converge. When driven, the fan 61 generates a gas flow from "intake" to "exhaust" through the adsorption line 101 to the module 11. This supplies atmospheric air into the module 11. A carbon dioxide concentration sensor 611, a humidity sensor 612, and a temperature sensor 613 are located in the gas exhaust portion of the adsorption line 101, and measure the carbon dioxide, humidity, and temperature exhausted from the adsorption line 101. Measurement information from the carbon dioxide concentration sensor 611, humidity sensor 612, and temperature sensor 613 is sent to the control device 90.

The vacuum line 102 branches off and connects to each of the modules 11. The vacuum pump 62 is located where the branched portions of the vacuum line 102 converge. When driven, the vacuum pump 62 draws in gas from inside the module 11 through the vacuum line 102, bringing the inside of the module 11 into a vacuum state or close to a vacuum state.

The carbon dioxide line 103 branches off and connects to each module 11. Where the branched portions of the carbon dioxide line 103 converge, a carbon dioxide capture pump 63, an intercooler 64, a separator 65, and a carbon dioxide tank 66 are located.

The carbon dioxide capture pump 63 applies suction force to send the carbon dioxide circulating through the carbon dioxide line 103 to the carbon dioxide tank 66. A one-way valve 631 is located upstream of the carbon dioxide capture pump 63 in the carbon dioxide line 103. This prevents gas from flowing back from the intercooler 64 side to the module 11 side.

The intercooler 64 is an intermediate cooling device that cools the high-temperature gas containing carbon dioxide recovered from the module 11 and separates it into gas and liquid.

The water separated into gas and liquid in the intercooler 64 is recovered in the separator 65. The separator 65 is equipped with a first valve 651 and a second valve 652. The first valve 651 opens and closes the path that connects to the gas phase of the separator 65. The second valve 652 opens and closes the path that connects to the liquid phase of the separator 65.

The carbon dioxide tank 66 stores the carbon dioxide recovered through the carbon dioxide line 103. A tank valve 661 is disposed upstream of the carbon dioxide tank 66 on the carbon dioxide line 103. The tank valve 661 is controlled to open and close by the control device 90. In addition, various sensors such as a pressure sensor 662, a flow rate sensor 663, a humidity sensor 664, a temperature sensor 665, and a carbon dioxide concentration sensor 666 are disposed between the tank valve 661 and the carbon dioxide tank 66 on the carbon dioxide line 103.

In addition to the carbon dioxide line 103, the carbon dioxide tank 66 is connected to a circulation line 104 that returns ballast to the carbon dioxide capture pump 63. A flow rate sensor 667 is installed in the circulation line 104. The carbon dioxide tank 66 is also equipped with a pressure relief valve 668 that releases pressure when the pressure exceeds a predetermined level.

Next, the inert gas tank 69 will be described. The inert gas tank 69 stores _N2 as an inert gas supplied from an _N2 gas cylinder 691 at a certain pressure or higher (for example, 980 kPa). A gas cylinder valve 692 is arranged between the inert gas tank 69 and the _N2 gas cylinder 691. The inert gas tank 69 is also arranged with a pressure release valve 693 that releases pressure when the pressure reaches a predetermined pressure or higher. A pressure sensor 694 is arranged inside the inert gas tank 69. Pressure information measured by the pressure sensor 694 is sent to the control device 90.

The inert gas tank 69 is connected to the carbon dioxide line 103 via the inert gas supply line 107. An inert gas valve 695 is disposed on the inert gas supply line 107. The opening and closing of the inert gas valve 695 is controlled by the control device 90.

The heat exchanger 70 will be described with reference to Figure 2. The heat exchanger 70 supplies thermal energy to heat the interior of each module 11 of the module unit 10 to a predetermined temperature when that module 11 performs the desorption process. The heat exchanger 70 also recovers unnecessary thermal energy when each module 11 performs the adsorption process.

The heat exchanger 70 of this embodiment includes a heat source circuit 80, a cold water line 111, a hot water line 112, a three-way valve 30, a bypass path 31, and a bypass valve 32.

The heat source circuit 80 mainly comprises a heat source device 81, a cold water tank 82, and a hot water tank 83, and performs heat exchange between the cooling heat medium flowing in the cold water line 111 and the heating heat medium flowing in the hot water line 112. The heat transfer that occurs in the heat source circuit 80 cools the heat medium flowing in the cold water line 111 and heats the heat medium flowing in the hot water line 112. The heat medium is, for example, a liquid such as water. The detailed configuration of the heat source circuit 80 will be described later with reference to Figure 5.

The chilled water line 111 is a pipe through which chilled water flows as a cooling heat medium. The chilled water line 111 is branched and connected to the upstream and downstream sides of each module 11, connecting the chilled water tank 82 to each module 11. Of the chilled water lines 111, the line connected to the upstream side of each module 11 is referred to as the chilled water supply line 111a, and the line connected to the downstream side of each module 11 is referred to as the chilled water return line 111b.

The chilled water supply line 111a is connected in parallel to multiple modules 11, allowing chilled water to be supplied to each module 11 in parallel. A first chilled water circulation water pump 822 and a second chilled water circulation water pump 823 are arranged on the chilled water supply line 111a. The first chilled water circulation water pump 822 and the second chilled water circulation water pump 823 are, for example, cascade pumps.

In addition, a circulation line 824 is arranged in the chilled water supply line 111a, returning from the downstream side of the second chilled water circulation water pump 823 to the upstream side. A safety valve 825 is arranged in this circulation line 824. The safety valve 825 relieves pressure when the pressure in the system between the second chilled water circulation water pump 823 and the chilled water line 111 exceeds a certain level, thereby suppressing pressure increases. By arranging the safety valve 825, which relieves pressure in the event of an abnormality in the chilled water line 111 system, in parallel with the second chilled water circulation water pump 823, it is possible to achieve both high flow rate circulation by the second chilled water circulation water pump 823 and safe operation.

The cold water recovery line 111b is also connected in parallel to multiple modules 11, allowing the recovery of cold water after cooling is complete to be carried out in parallel for each module 11.

The hot water line 112 is a pipe through which hot water flows as a heat medium for heating. The hot water line 112 branches off and is connected to the upstream and downstream sides of each module 11, connecting the hot water tank 83 to each module 11. Of the hot water lines 112, the line connected to the upstream side of each module 11 is referred to as the hot water supply line 112a, and the line connected to the downstream side of each module 11 is referred to as the hot water return line 112b.

The hot water supply line 112a is connected in parallel to multiple modules 11, allowing hot water to be supplied to each module 11 in parallel. A first hot water circulation water pump 832 and a second hot water circulation water pump 833 are arranged on the hot water supply line 112a. The first hot water circulation water pump 832 and the second hot water circulation water pump 833 are, for example, cascade pumps. By using a cascade pump that generates a large amount of heat when driven, it is possible to further heat the heat medium passing through the first hot water circulation water pump 832 and the second hot water circulation water pump 833.

In addition, a circulation line 834 is arranged in the hot water supply line 112a, returning from the downstream side of the second hot water circulation water pump 833 to the upstream side. A safety valve 835 is arranged in this circulation line 834. The safety valve 835 relieves pressure when the pressure in the system between the second hot water circulation water pump 833 and the hot water line 112 exceeds a certain level, thereby suppressing pressure increases. By arranging the safety valve 835, which relieves pressure in the event of an abnormality in the hot water line 112 system, in parallel with the second hot water circulation water pump 833, it is possible to achieve both high flow rate circulation by the second hot water circulation water pump 833 and safe operation.

The hot water return line 112b is also connected in parallel to multiple modules 11, allowing the recovery of hot water after heating is complete to be carried out in parallel for each module 11.

The three-way valve 30 is connected to the cold water line 111, the hot water line 112, and the module 11. The three-way valve 30 is located on both the upstream and downstream sides of the module 11. The three-way valve 30 is configured to be able to select, by switching the flow path, between a cold water connection state that connects the cold water line 111 and the module 11, a hot water connection state that connects the hot water line 112 and the module 11, and a cut-off state that cuts off the connection between the cold water line 111 and the hot water line 112 and the module 11.

The flow path switching of the three-way valve 30 is controlled by the control device 90. The heat medium is introduced into the module 11 through the three-way valve 30 located upstream, and the heat medium is returned to the heat source device 81 through the three-way valve 30 located downstream.

The bypass path 31 is a flow path that allows the movement of heat transfer medium between modules 11. The bypass path 31 connects two modules 11. The modules 11 connected by the bypass path 31 may be adjacent modules, or may be non-adjacent modules 11 located at a distance.

A bypass valve 32 is arranged in the bypass path 31. A bypass valve 32 is arranged in each of the multiple bypass paths 31. The bypass valves 32 are controlled to open and close by the control device 90.

Figure 4 is a schematic diagram showing the configuration related to the liquid flow in module 11 of the carbon dioxide capture device 1 of this embodiment. In the following description, the three-way valve 30 located upstream of module 11 will be referred to as three-way valve 30a, and the three-way valve 30 located downstream of module 11 will be referred to as three-way valve 30b.

As shown in FIG. 4, the module 11 has an inlet-side flow path 33 connected to an inlet through which the heat medium flows in, and an outlet-side flow path 34 connected to an outlet through which the heat medium flows out. The bypass path 31 is connected to the outlet-side flow path 34 of the module 11 and is also connected to the inlet-side flow path 33 of another module 11.

A three-way valve 30a is disposed at the upstream end of the inlet flow path 33, and a three-way valve 30b is disposed at the downstream end of the outlet flow path 34. When connected to hot water, the three-way valve 30a is connected to the hot water supply line 112a, and the three-way valve 30b is connected to the hot water return line 112b. When connected to cold water, the three-way valve 30a is connected to the cold water supply line 111a, and the three-way valve 30b is connected to the cold water return line 111b.

Three-way valves 30a and 30b are configured to allow for flow rate adjustment. This flow rate adjustment function allows for adjustment of the hot water flow rate when hot water is connected, and for adjustment of the cold water flow rate when cold water is connected.

A temperature sensor 35 is arranged in the inlet flow path 33. A temperature sensor 36 and a flow rate sensor 37 are arranged in the outlet flow path 34. Measurement information from the temperature sensor 35, temperature sensor 36, and flow rate sensor 37 is sent to the control device 90.

Next, the control device 90 will be described. The control device 90 controls the operation of each part of the carbon dioxide capture device 1. The control device 90 controls the operation of devices used for carbon dioxide adsorption and desorption, such as driving and stopping. The control device 90 selectively controls the timing of supplying heat medium to each module 11 to heat or cool the modules 11, so that the multiple modules 11 repeatedly adsorb and desorb in time series.

The control device 90 controls the opening and closing of the first valve 21, second valve 22, third valve 23, and fourth valve 24 provided in each module 11, as well as the opening and closing of each bypass valve 32. The control device 90 also controls the operation of the fan 61, vacuum pump 62, carbon dioxide capture pump 63, first cold water circulation water pump 822, second cold water circulation water pump 823, first hot water circulation water pump 832, second hot water circulation water pump 833, etc., and controls the opening and closing of the safety valve 825 and safety valve 835.

The control device 90 is a computer having, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. The control device 90 may consist of one unit or multiple units. The control device 90 may also be configured using electrical circuits such as relays.

<Carbon dioxide capture>
Next, we will explain the control for capturing carbon dioxide by the control device 90. The carbon dioxide capture device 1 alternately performs an adsorption process in which the adsorbent 12 in the module 11 adsorbs carbon dioxide in a gas such as the air that has been taken in, and a desorption process in which the carbon dioxide adsorbed by the adsorbent 12 is desorbed, and stores the desorbed carbon dioxide in the carbon dioxide tank 66, thereby removing and capturing carbon dioxide from the air.

The adsorption process is a process in which carbon dioxide is adsorbed by the adsorbent 12 in the module 11. During the adsorption process, the third valve 23 and fourth valve 24 of the module 11 are opened, and the first valve 21 and second valve 22 are closed. In addition to controlling the valve opening and closing, the heat exchanger 70 controls the three-way valves 30a and 30b to a cold water connection state, allowing cold water to flow through the module 11 and cool the adsorbent 12 in the module 11. The fan 61 is driven, creating a gas flow from upstream to downstream, and gas containing carbon dioxide (e.g., atmospheric air) is drawn in through the third valve 23. The drawn gas passes through the adsorbent 12 in the module 11. At this time, the temperature inside the module 11 is kept at room temperature (25°C) due to the cooling of the cold water, and the carbon dioxide in the gas is adsorbed by the adsorbent 12. Gases other than carbon dioxide, such as nitrogen and oxygen, are exhausted to the outside of the carbon dioxide capture device 1 through the fourth valve 24 and the adsorption line 101.

The desorption process is a process of desorbing carbon dioxide from the adsorbent 12 in the module 11. During the desorption process, the first valve 21, third valve 23, and fourth valve 24 of the module 11 are closed, and the second valve 22 is opened. The vacuum pump 62 is operated to draw air into the interior of the module 11, reducing the pressure and creating a vacuum or near-vacuum state. In addition to controlling the opening and closing of the valves, the heat exchanger 70 controls the three-way valves 30a and 30b to a hot water connection state, allowing hot water to flow through the module 11, supplying thermal energy and raising the temperature of the adsorbent 12 in the module 11. By controlling the temperature rise of the adsorbent 12, the adsorbent 12 is also heated to a predetermined temperature (e.g., 80°C) sufficient for the desorption process, and the carbon dioxide adsorbed in the adsorbent 12 is desorbed. Next, the second valve 22, the third valve 23, and the fourth valve 24 are closed, the first valve 21 is opened, the carbon dioxide recovery pump 63 is driven, and the carbon dioxide desorbed through the carbon dioxide line 103 is stored in the carbon dioxide tank 66. In this embodiment, each process is controlled so that 12 of the 16 modules 11 perform the adsorption process and the remaining 4 perform the desorption process.

<Heat source circuit>
Next, the detailed configuration of the heat source circuit 80 will be described with reference to Fig. 5. Fig. 5 is a schematic diagram showing the configuration of the heat source circuit 80 of the carbon dioxide recovery device 1 of this embodiment.

As shown in FIG. 5, the heat source circuit 80 of this embodiment includes a heat source unit 81, a heat source high-temperature water circuit 85 including a hot water tank 83, a heat source low-temperature water circuit 86 including a cold water tank 82, and a reservoir tank 88.

The heat source 81 cools the heat medium introduced from the cold water tank 82 and heats the medium introduced from the hot water tank 83. The heat source 81 compresses and expands gas using a heat pump, and transfers the generated cold and hot heat to perform cooling and heating.

The heat source high-temperature water circuit 85 circulates hot water between the hot water tank 83 and the heat source unit 81. The heat source high-temperature water circuit 85 includes the hot water tank 83, a hot water side heat source supply line 221, and a hot water side heat source return line 222.

The hot water tank 83 is a heat storage device with thermal insulation capabilities that can store a heat transfer medium. The capacity of the hot water tank 83 is preferably at least five times the maximum flow rate discharged by the hot water circulation water pump 831 (described below). By setting the capacity of the hot water tank 83 to a value greater than the flow rate of the heat transfer medium, it is possible to suppress fluctuations in the temperature of the hot water (heat transfer medium) during heat load fluctuations within a specified temperature range (for example, within ±5°C). In other words, the hot water tank 83 functions as a buffer for heat load fluctuations.

A temperature sensor 830 for measuring the temperature of the heat medium is disposed inside the hot water tank 83. The measurement results of the temperature sensor 830 are output to the control device 90. The hot water tank 83 is connected to the heat source device 81 via the hot water side heat source supply line 221 and the hot water side heat source return line 222.

The hot water side heat source supply line 221 is a path along which the heat medium flows from the hot water tank 83 to the heat source device 81. The hot water side heat source supply line 221 is equipped with a valve 301, a hot water side circulation water pump 831, a flow rate sensor 231, and a temperature sensor 232, arranged in this order from upstream to downstream. The hot water side circulation water pump 831 is configured, for example, by a centrifugal pump, and circulates the heat medium between the hot water tank 83 and the heat source device 81. The flow rate sensor 231 measures the flow rate of the heat medium flowing into the heat source device 81 and outputs the measurement result to the control device 90. The temperature sensor 233 measures the temperature of the heat medium flowing into the heat source device 81 and outputs the measurement result to the control device 90.

The hot water side heat source return line 222 is a path along which the heat medium flows from the heat source device 81 to the hot water tank 83. A temperature sensor 233 and a valve 302 are arranged in this order from upstream to downstream on the hot water side heat source return line 222. The temperature sensor 233 measures the temperature of the hot water flowing out from the heat source device 81 and outputs the measurement result to the control device 90.

The hot water tank 83 is connected to the hot water supply line 112a and the hot water return line 112b. Valve 305, water filter 234, and valve 306 are located on the hot water supply line 112a near the hot water tank 83. Valves 303 and 304 are located on the hot water return line 112b.

The connection positions (port positions) of each line in the hot water tank 83 are preferably set taking into consideration the temperature stratification of the heat medium (hot water) stored in the hot water tank 83. Figure 6 is a schematic diagram showing the connection positions of each line connected to the hot water tank 83.

As shown in Figure 6, the hot water stored in the hot water tank 83 is temperature stratified, with the temperature higher in the upper layers and lower in the lower layers. The connection positions of each line in the hot water tank 83 are set to be, in order from highest to lowest, the hot water side heat source return line 222, the hot water supply line 112a, the hot water side heat source supply line 221, and the hot water return line 112b.

The hot water side heat source return line 222 is a pipe that returns hot water (e.g., 82°C) heated by the heat source device 81, and returns it to the highest temperature part in the temperature stratification. The hot water supply line 112a is connected to the next highest position after the connection position of the hot water side heat source return line 222, so the hot water heated by the heat source device 81 is sent upstream of the module 11 while maintaining a high temperature (e.g., 80°C) without significantly reducing its temperature.

The hot water side heat source supply line 221 is a pipe used to send hot water to be heated to the heat source device 81, and is connected at the next highest connection position after the hot water supply line 112a. This allows high-temperature hot water to be sent through the hot water supply line 112a, while hot water maintained at a relatively high temperature (e.g., 75°C) by the hot water side heat source supply line 221 can be sent to the heat source device 81. The hot water return line 112b is a pipe that returns hot water at the relatively lowest temperature (e.g., 72°C) after heating the module 11. Because the hot water return line 112b is connected at the lowest position, the amount of low-temperature hot water mixed into the hot water supply line 112a, which requires a high temperature, can be reduced.

Next, returning to Figure 5, the heat source low-temperature water circuit 86 will be described. The heat source low-temperature water circuit 86 circulates cold water between the cold water tank 82 and the heat source unit 81. The heat source low-temperature water circuit 86 includes the cold water tank 82, a cold water side heat source supply line 121, and a cold water side heat source return line 122.

The cold water tank 82 is a heat storage device with thermal insulation capabilities that can store a heat transfer medium. The capacity of the cold water tank 82 is preferably at least five times the maximum flow rate discharged by the cold water circulation water pump 821 (described below). By setting the capacity of the cold water tank 82 to a value greater than the flow rate of the heat transfer medium, it is possible to suppress fluctuations in the temperature of the cold water (heat transfer medium) during thermal load fluctuations within a specified temperature range (for example, within ±5°C). In other words, the cold water tank 82 functions as a buffer for thermal load fluctuations.

A temperature sensor 820 for measuring the temperature of the heat medium is disposed inside the cold water tank 82. The measurement results of the temperature sensor 820 are output to the control device 90. The cold water tank 82 is connected to the heat source device 81 via a cold water side heat source supply line 121 and a cold water side heat source return line 122.

The chilled water side heat source supply line 121 is a path along which the heat medium flows from the chilled water tank 82 to the heat source device 81. The chilled water side heat source supply line 121 is equipped with a valve 307, a chilled water side circulation water pump 821, a flow rate sensor 131, and a temperature sensor 132. The chilled water side circulation water pump 821 is configured, for example, by a centrifugal pump, and circulates the heat medium between the chilled water tank 82 and the heat source device 81. The flow rate sensor 131 measures the flow rate of the heat medium flowing into the heat source device 81 and outputs the measurement result to the control device 90. The temperature sensor 132 measures the temperature of the heat medium flowing into the heat source device 81 and outputs the measurement result to the control device 90.

In addition, the chilled water side heat source supply line 121 is connected to a radiator bypass line 123 for cooling the heat medium and a heater bypass line 124 for heating the heat medium. The radiator bypass line 123 and heater bypass line 124 are temperature adjustment circuits that adjust the temperature of the heat medium flowing into the heat source unit 81 to an operable temperature when the outside air temperature or heat load fluctuates.

The radiator bypass line 123 is connected between the chilled water circulation water pump 821 and the flow rate sensor 131 in the chilled water heat source supply line 121. A valve 141 and a radiator fan 142 are arranged in the radiator bypass line 123. The valve 141 can open and close the flow path and adjust the flow rate based on control signals from the control device 90. The radiator fan 142 is a heat dissipation device that cools the heat medium passing through the radiator bypass line 123. The heat medium is cooled by the radiator bypass line 123 mainly during high temperatures, such as in the summer. By cooling the heat medium through the radiator bypass line 123, the temperature of the chilled water introduced into the heat source device 81 is controlled to be below a preset threshold.

The heater bypass line 124 is located in the chilled water heat source supply line 121 between the chilled water circulation water pump 821 and the flow rate sensor 131, and is connected to the inside of the radiator bypass line 123. A valve 308 and a heater 150 are arranged in the heater bypass line 124. The heater 150 is driven by a control signal or a relay drive signal from the control device 90, and heats the heat medium flowing through the heater bypass line 124. Heating of the heat medium by the heater bypass line 124 is mainly performed when the temperature is low, such as during start-up in winter. By heating the heat medium by the heater bypass line 124, the temperature of the heat medium introduced into the heat source device 81 is controlled to be above a preset threshold.

The chilled water side heat source return line 122 is a path along which the heat medium flows from the heat source device 81 to the chilled water tank 82. The chilled water side heat source return line 122 is equipped with a temperature sensor 133, valves 309, 310, 311, and 312, arranged in this order from upstream to downstream. The temperature sensor 132 measures the temperature of the chilled water flowing out from the heat source device 81 and outputs the measurement result to the control device 90.

The cold water tank 82 is connected to the cold water supply line 111a and the cold water return line 111b. Valve 315, water filter 134, and valve 316 are located on the cold water supply line 111a near the cold water tank 82. Valves 313 and 314 are located on the cold water return line 111b.

The connection positions (port positions) of each line in the chilled water tank 82 are preferably set taking into consideration the temperature stratification of the heat transfer medium (chilled water) stored in the chilled water tank 82. Figure 7 is a schematic diagram showing the connection positions of each line connected to the chilled water tank 82.

As shown in Figure 7, the chilled water stored in the chilled water tank 82 is thermally stratified, with the temperature higher in the upper layers and lower in the lower layers. The connection positions of each line in the chilled water tank 82 are set to be, in order from highest to lowest, chilled water return line 111b, chilled water side heat source return line 122, chilled water supply line 111a, and chilled water side heat source supply line 121.

The cold water return line 111b is a pipe that returns cold water at the relatively highest temperature (e.g., 36°C) after cooling the module 11. Because the cold water return line 111b is connected at the highest position, it is possible to prevent high-temperature cold water from mixing with the cold water sent out from the cold water supply line 111a. The cold water side heat source return line 122 is a pipe that returns cold water (e.g., 30°C) cooled by the heat source device 81, and is connected at the next highest position after the connection position of the cold water return line 111b. The cold water that returns via the cold water side heat source return line 122 moves to the lower side of the temperature stratification.

The chilled water supply line 111a is connected at the next highest point after the chilled water heat source return line 122, so it sends out the chilled water cooled by the heat source device 81 to the upstream side of the module 11 while maintaining a low temperature (e.g., 31°C) without significantly increasing the temperature. The chilled water supply line 121 is connected at the lowest point, so it sends out low-temperature (e.g., 33°C) chilled water that was not sent from the chilled water supply line 111a to the module 11 to the heat source device 81.

Next, returning to Figure 5, we will explain the equipment heat recovery circuit 87, which cools the target equipment, such as the intercooler 64, vacuum pump 62, and carbon dioxide recovery pump 63, included in the heat source low-temperature water circuit 86, and raises the temperature of the heat medium.

The equipment heat recovery circuit 87 is connected in parallel to the heat source low-temperature water circuit 86. In this embodiment, the equipment heat recovery circuit 87 includes a first equipment thermal cooling line 126 that exchanges heat with the intercooler 64, and a second equipment thermal cooling line 127 that exchanges heat with the vacuum pump 62 and the carbon dioxide recovery pump 63.

The upstream end of the first equipment thermal cooling line 126 is connected to the chilled water side heat source return line 122, and the downstream end is connected to the chilled water side heat source supply line 121. In this embodiment, the connection point of the upstream end of the first equipment thermal cooling line 126 is between valves 309 and 310 on the chilled water side heat source return line 122. The connection point of the lower end of the first equipment thermal cooling line 126 is between valve 307 on the chilled water side heat source supply line 121 and the chilled water side circulation water pump 821.

The first equipment heat cooling line 126 is connected to the intercooler 64, which generates steam condensation heat, and cools the intercooler 64 with cold water to recover the steam condensation heat as waste heat. The cold water is heated by heat exchange with the intercooler 64 and then sent to the cold water heat source return line 121.

A flow rate sensor 841 and a temperature sensor 842 are arranged upstream of the intercooler 64 on the first equipment thermal cooling line 126, and a temperature sensor 843 and a valve 317 are arranged downstream of the intercooler 64. The flow rate sensor 841 measures the flow rate of the heat medium before heat exchange with the intercooler 64 and outputs the measurement result to the control device 90. The temperature sensor 842 measures the temperature of the heat medium before heat exchange with the intercooler 64 and outputs the measurement result to the control device 90. The temperature sensor 843 measures the temperature of the heat medium after heat exchange with the intercooler 64 and outputs the measurement result to the control device 90.

The second equipment thermal cooling line 127 has its upstream end connected to the chilled water heat source return line 122 and its downstream end connected to the chilled water heat source supply line 121. In this embodiment, the connection point of the upstream end of the second equipment thermal cooling line 127 is between valve 310 and valve 311 on the chilled water heat source return line 122. The connection point of the lower end of the second equipment thermal cooling line 127 is between valve 307 and chilled water circulation water pump 821 on the chilled water side heat source supply line 121, which is upstream of the connection point of the downstream end of the first equipment thermal cooling line 126.

In addition, the second equipment thermal cooling line 127 in this embodiment includes a first branch line 127a that cools the vacuum pump 62 and a second branch line 127b that cools the carbon dioxide capture pump 63.

The first branch line 127a is connected to the vacuum pump 62 and cools the vacuum pump 62 with cold water. The heat medium is heated by heat exchange with the vacuum pump 62 and then merges with the second branch line 127b, where it is sent to the cold water heat source supply line 121.

A flow rate sensor 851 and a temperature sensor 852 are arranged upstream of the vacuum pump 62 on the first branch line 127a, and a temperature sensor 853 is arranged downstream of the vacuum pump 62. The flow rate sensor 851 measures the flow rate of the heat medium before heat exchange with the vacuum pump 62 and outputs the measurement result to the control device 90. The temperature sensor 852 measures the temperature of the heat medium before heat exchange with the vacuum pump 62 and outputs the measurement result to the control device 90. The temperature sensor 853 measures the temperature of the chilled water after heat exchange with the vacuum pump 62 and outputs the measurement result to the control device 90.

The second branch line 127b is connected to the carbon dioxide capture pump 63 and cools the carbon dioxide capture pump 63 using a heat medium. The heat medium is heated by heat exchange with the carbon dioxide capture pump 63 and then merges with the first branch line 127a, where it is sent to the chilled water heat source supply line 121.

A flow rate sensor 861 and a temperature sensor 862 are arranged upstream of the carbon dioxide capture pump 63 on the second branch line 127b, and a temperature sensor 863 is arranged downstream of the carbon dioxide capture pump 63. The flow rate sensor 861 measures the flow rate of the heat medium before heat exchange with the carbon dioxide capture pump 63 and outputs the measurement result to the control device 90. The temperature sensor 862 measures the temperature of the heat medium before heat exchange with the carbon dioxide capture pump 63 and outputs the measurement result to the control device 90. The temperature sensor 863 measures the temperature of the heat medium after heat exchange with the carbon dioxide capture pump 63 and outputs the measurement result to the control device 90.

An equipment cooling pump 870 is disposed upstream of the branch point of the first branch line 127a and the second branch line 127b in the second equipment thermal cooling line 127. Furthermore, valves 318 and 319 are disposed downstream of the junction of the first branch line 127a and the second branch line 127b in the second equipment thermal cooling line 127.

In this embodiment, the equipment cooling pump 870 is composed of a cascade pump with sufficient head to pump the heat medium without being hindered by the high pressure loss of the vacuum pump 62 and carbon dioxide capture pump 63, which are the target equipment for heat recovery. The heat generated by driving the equipment cooling pump 870 is also recovered as exhaust heat using cold water.

As explained above, the equipment heat recovery circuit 87 recovers the heat of steam condensation from the intercooler 64 and the exhaust heat from the vacuum pump 62 and carbon dioxide recovery pump 63 into a heat medium to cool the target equipment, and the heat recovery enables the heat medium to flow into the heat source device 81 at a high temperature potential.

The equipment heat recovery circuit 87 uses the low-temperature heat medium cooled by the heat source device 81 to cool the target equipment, which are the vacuum pump 62, carbon dioxide capture pump 63, and intercooler 64. After cooling the target equipment (vacuum pump 62, carbon dioxide capture pump 63, and intercooler 64) and recovering the exhaust heat, the chilled water merges with the chilled water side heat source supply line 121, through which chilled water discharged from the chilled water tank 82 (for example, the upper temperature location of the chilled water tank 82) flows, and is introduced into the heat source device 81. After recovering the exhaust heat, the chilled water is heated to an appropriate temperature range.

In this embodiment, the radiator bypass line 123 for cooling the cold water or the heater bypass line 124 for heating the cold water further adjusts the temperature to an appropriate range before entering the heat source device 81. This makes it possible to smooth out heat fluctuations over time and maintain a constant inflow temperature to the heat source device 81, even during operation with large fluctuations in the heat load.

Next, the configuration of the reservoir tank 88 will be described. The reservoir tank 88 is a tank capable of storing a heat transfer medium. The reservoir tank 88 is connected to the hot water tank 83 and the cold water tank 82. A valve 320 is arranged between the reservoir tank 88 and the hot water tank 83, and another valve 320 is arranged between the reservoir tank 88 and the cold water tank 82. When the amount of heat transfer medium stored in the hot water tank 83 needs to be adjusted, the valve 320 is opened, and the heat transfer medium is transferred between the reservoir tank 88 and the hot water tank 83. Similarly, when the amount of heat transfer medium stored in the cold water tank 82 needs to be adjusted, the valve 321 is opened, and the heat transfer medium is transferred between the reservoir tank 88 and the cold water tank 82. A level sensor 880 is arranged inside the reservoir tank 88 to monitor the amount of storage. The measurement results of the level sensor 880 are output to the control device 90. The control device 90 uses the measurement results of the level sensor 880 to determine whether the reservoir tank 88 can be used.

<Equipment heat recovery control>
The control device 90 acquires the output signals of the flow rate sensor 231 and the temperature sensor 232 to monitor the flow rate and temperature of the hot water flowing into the heat source device 81, and acquires the output signals of the flow rate sensor 131 and the temperature sensor 132 to monitor the flow rate and temperature of the cold water flowing into the heat source device 81.

The control device 90 also monitors the flow rate, inlet temperature, and outlet temperature of the chilled water flowing into the target equipment. More specifically, the control device 90 acquires output signals from flow rate sensor 841, temperature sensor 842, and temperature sensor 843 to acquire the flow rate and temperature of the chilled water flowing into the intercooler 64, as well as the outlet temperature of the chilled water after cooling by the intercooler 64. The control device 90 also acquires output signals from flow rate sensor 851, temperature sensor 852, and temperature sensor 853 to acquire the flow rate and temperature of the chilled water flowing into the vacuum pump 62, as well as the outlet temperature of the chilled water after cooling by the vacuum pump 62. The control device 90 also acquires output signals from flow rate sensor 861, temperature sensor 862, and temperature sensor 863 to acquire the flow rate and temperature of the chilled water flowing into the carbon dioxide capture pump 63, as well as the outlet temperature of the chilled water after cooling by the carbon dioxide capture pump 63.

The control device 90 controls the opening and closing of valves 301-321 and adjusts the flow rate based on various monitor results. For example, if the temperature of the chilled water flowing into the heat source device 81 is low, it controls valves 317-319 to increase the amount of chilled water flowing into the target equipment (vacuum pump 62, carbon dioxide capture pump 63, and intercooler 64) and raise the temperature of the chilled water. In this case, it is preferable to control the flow rate or opening and closing so that the temperature does not deviate from the desired temperature range set for the target equipment.

As such, the carbon dioxide recovery device 1 of this embodiment further includes a control device 90 that controls the path of the equipment heat recovery circuit 87 so that the temperature of the cooling heat medium flowing into the heat source device 81 is within a predetermined appropriate range.

This allows the carbon dioxide capture device 1 to adapt to thermal fluctuations caused by changes in the external environment, etc., and achieves a more energy-efficient configuration.

In this embodiment, the valves 301 to 321 are configured to be automatically controlled by the control device 90, but if automatic control is not required, manual valves may also be used.

As explained above, the carbon dioxide capture device 1 of this embodiment includes a plurality of modules 11 that have adsorbents 12 therein and perform an adsorption process in which a gas containing carbon dioxide is drawn into the adsorbent 12 to adsorb the carbon dioxide, and a desorption process in which the adsorbent 12 is heated under reduced pressure to desorb carbon dioxide from the adsorbent 12; a heat pump-type heat source 81 that heats hot water and cools cold water; and a heat exchanger 70 that has a hot water line (heating heat medium line) 112 that supplies hot water (heating heat medium) to each of the modules 11 for heating, and a cold water line (cooling heat medium line) 111 that supplies cold water (cooling heat medium) for cooling, and the heat exchanger 7 0 includes a hot water tank (heating heat medium tank) 83 that stores hot water heated by a heat source device 81 and a heat-source high-temperature water circuit 85 that circulates hot water between the hot water tank 83 and the heat source device 81; a cold water tank (cooling heat medium tank) 82 that stores cold water cooled by the heat source device 81 and a heat-source low-temperature water circuit 86 that circulates cold water between the cold water tank 82 and the heat source device 81; and an equipment heat recovery circuit 87 that branches off from the heat-source low-temperature water circuit 86 and is connected to the inlet side of the heat source device 81 of the heat-source low-temperature water circuit 86 via target equipment (vacuum pump 62, carbon dioxide recovery pump 63, intercooler 64, etc.) that performs the adsorption process or desorption process, and returns cold water that has recovered exhaust heat from the target equipment to the heat source device 81.

This allows for both the generation of high-temperature heat and the cooling of the target equipment, while also reducing the temperature difference in the heat source device 81 through the heat exhaust effect of the equipment heat recovery circuit 87, resulting in a high COP and reducing the amount of power required. Figure 8 is a graph schematically illustrating the relationship between the temperature difference in the heat medium introduced into the heat source device 81 and COP. As shown in Figure 8, the greater the temperature difference between the high-temperature and low-temperature heat medium introduced into the heat source device 81, the lower the COP. For example, when heat exchange is performed between a warm heat medium and a low-temperature heat medium in an environment with a low outside air temperature, the temperature difference between the high-temperature and low-temperature heat medium increases, resulting in a lower COP. In this regard, the configuration of this embodiment allows the target equipment to be cooled using a low-temperature heat medium, and the heat medium warmed by this cooling can be flowed into the low-temperature side of the heat source device 81, thereby improving the COP.

In addition, in this embodiment, the cold water used to cool the module 11 and recover the exhaust heat is returned to the inlet side of the heat source device 81 via the cold water tank 82.

This allows the exhaust heat generated when cooling the module 11 to be used to raise the temperature of the cold water flowing into the heat source device 81, thereby efficiently improving the COP.

In addition, the carbon dioxide capture device 1 of this embodiment further includes an equipment cooling pump 870 as a cascade pump that sends the cooling heat medium to the inlet side of the heat source device 81.

As a result, since the equipment is configured with a cascade pump that generates more heat than other types of pumps, the exhaust heat of the equipment cooling pump 870 itself can also be used to efficiently heat the cold water flowing into the heat source device 81.

In addition, in this embodiment, the equipment heat recovery circuit 87 is configured such that target equipment (such as a vacuum pump 62, a carbon dioxide recovery pump 63, and an intercooler 64) is arranged on each of the multiple paths (first equipment heat cooling line 126, second equipment heat cooling line 127) branching off from the heat source low-temperature water circuit 86, and the cold water that has recovered exhaust heat from each of the multiple target equipment is collected and returned to the heat source device 81.

This allows each device to be cooled to the appropriate temperature while recovering exhaust heat, resulting in more energy-efficient system operation.

In the above embodiment, the target devices, namely the vacuum pump 62, the carbon dioxide capture pump 63, and the intercooler 64, are arranged in parallel on the device heat recovery circuit 87, but this configuration is not limited to this. The target devices can also be arranged in series on the device heat recovery circuit 87. When arranging the target devices in series on the device heat recovery circuit 87, for example, if the heat medium after heat recovery can condense the water vapor in the intercooler 64, the vacuum pump 62 and the carbon dioxide capture pump 63 can be arranged upstream and the intercooler 64 can be arranged downstream. In this configuration, the vacuum pump 62 and the carbon dioxide capture pump 63, which require a lower temperature heat medium than the intercooler 64, are cooled first. Therefore, the intercooler 64 can also be cooled with the heat medium after cooling the vacuum pump 62 and the carbon dioxide capture pump 63. By preferentially supplying a lower temperature heat medium to the device requiring the lowest temperature cooling, sufficient cooling performance can be achieved. With this configuration, the heat medium heated by the intercooler 64 can also be introduced into the inlet side of the heat source 81.

The above describes embodiments of the present invention, but the present invention is not limited to the above-mentioned embodiments and variations. Furthermore, the effects described in the above embodiments are merely a list of preferred effects, and are not limited to those described in the above embodiments.

1 Carbon dioxide capture device 11 Module 12 Adsorbent 62 Vacuum pump (target equipment)
63 Carbon dioxide capture pump (target equipment)
64 Intercooler (target equipment)
70 Heat exchange device 80 Heat source circuit 81 Heat source device 82 Cold water tank (cooling heat medium tank)
83 Hot water tank (heating medium tank)
85 Heat source high temperature water circuit 86 Heat source low temperature water circuit 87 Equipment heat recovery circuit 90 Control device 111 Cold water line (cooling heat medium line)
111a Cold water outgoing line (cooling heat medium outgoing line)
111b Cold water return line (cooling heat medium return line)
112 Hot water line (heating medium line)
112a Hot water outgoing line (heating medium outgoing line)
112b Hot water return line (heating medium return line)
870 Equipment cooling pump (cascade pump)

Claims (5)

a plurality of modules each having an adsorbent therein, each performing an adsorption step of drawing a gas containing carbon dioxide into the adsorbent to adsorb the carbon dioxide, and a desorption step of heating the adsorbent under a reduced pressure around the adsorbent to desorb the carbon dioxide from the adsorbent;
a heat pump type heat source unit that heats a heating heat medium and cools a cooling heat medium, a heat exchange device having a heating heat medium line that supplies the heating heat medium to each of the modules for heating, and a cooling heat medium line that supplies the cooling heat medium to each of the modules for cooling;
Equipped with
The heat exchange device is
a heat source high-temperature water circuit including a heating heat medium tank that stores the heating heat medium heated by the heat source device, and circulating the heating heat medium between the heating heat medium tank and the heat source device;
a heat source low-temperature water circuit including a cooling heat medium tank that stores the cooling heat medium cooled by the heat source device, and circulating the cooling heat medium between the cooling heat medium tank and the heat source device;
an equipment heat recovery circuit that branches off from the heat-source low-temperature water circuit, passes through a target device for performing the adsorption process or the desorption process, and is connected to the inlet side of the heat-source low-temperature water circuit to the heat source device, and returns the cooling heat medium that has recovered exhaust heat from the target device to the heat source device;
having
Carbon dioxide capture equipment. the cooling heat medium after cooling the module and recovering the exhaust heat is returned to the inlet side of the heat source device via the cooling heat medium tank.
The carbon dioxide capture device according to claim 1 . The cooling system further includes a cascade pump that sends the cooling heat medium to an inlet side of the heat source device.
The carbon dioxide recovery device according to claim 1 or 2. The equipment heat recovery circuit includes:
the target devices are arranged in each of a plurality of paths branching from the heat-source low-temperature water circuit,
the cooling heat medium from which the exhaust heat has been recovered in each of the plurality of target devices is collected and returned to the heat source device;
The carbon dioxide recovery device according to claim 1 or 2. a control device that controls a path of the equipment heat recovery circuit so that the temperature of the cooling heat medium flowing into the heat source device is within a predetermined appropriate range;
The carbon dioxide recovery device according to claim 1 or 2.